It is known to provide a plug-in electric vehicle (PEV) or plug-in hybrid electric vehicle (PHEV) having a battery that may be charged when the vehicle is connected to a charging station. Charging stations are typically provided with a cable and charging plug which may be connected to a corresponding socket of the vehicle. In some countries, the cost of a given unit of electricity depends on the time of day, the cost being higher at certain times of day (such as during normal working hours) compared with other times. It is desirable to take advantage of reduced electricity costs where possible in order to reduce an overall running cost of a PEV or PHEV.